Use of HPLC in the identification of cis and trans-diaquabis(2,2 ′-bipyridine)ruthenium(II) complexes: crystal structure of cis-[Ru(H 2O) 2(bpy) 2](PF 6) 2

Abstract

[Ru(H 2O) 2(bpy) 2](PF 6) 2 complex was obtained by reacting HPF 6 in a [Ru(CO 3)(bpy) 2] aqueous solution. The complex can exist as cis and trans isomers and usually has been used in the preparation of several ruthenium–bipyridine species. Despite the possibility to have contamination of a specie in another, there is no analytical control involving the characterization of both complexes. Based on this we have proposed the use of high-performance liquid chromatography (HPLC) as an analytical technique to control the purity of cis and trans isomers. The separation was performed using a CLC-ODS column. The cis isomer eluted at 9.4 min while trans isomer eluted at 4.3 min. In aqueous solution the trans and cis isomer configurations were confirmed by NMR spectra ( 1H). The attribution of cis isomer was also made based on the X-ray crystal structure (monoclinic, P2 1/c, a=12.320(2), b=13.852(2), c=34.220(3) Å, β=91.89(1)°, Z=8) which is reported. The six-coordinated ruthenium atom is chelated by two bipyridines and two molecules of H 2O.